Hi! I am new to Chimera and I am trying to modify the PDB file of a peptide by acylation. I have also a PDB file for the fatty acid which I got by removing the bound protein. I used the join models to form a peptide bond but prompted with this error: The following problems occurred while reading PDB file for anomt1.pdbStart residue of secondary structure not found: HELIX 1 1 LEU 2 LEU 10 1 8Model 1 (anomt1.pdb) appears to be a protein without secondary structure assignments.Automatically computing assignments using 'ksdssp' and parameter values: energy cutoff -0.5 minimum helix length 3 minimum strand length 3Use command 'help ksdssp' for more information.TypeError Exception in Tk callback Function: <bound method BuildStructureDialog._addParamBond of <BuildStructure.gui.BuildStructureDialog object at 0x04F9FBF0>> (type: <type 'instancemethod'>) Args: ()Traceback (innermost last): File "C:\Program Files\Chimera 1.10.1\bin\lib\site-packages\Pmw\Pmw_1_3_3\lib\PmwBase.py", line 1747, in __call__ return apply(self.func, args) File "C:\Program Files\Chimera 1.10.1\share\BuildStructure\gui.py", line 313, in _addParamBond self._appbDihedral.get(), phi=self._appbPhi.get()) File "C:\Program Files\Chimera 1.10.1\share\BuildStructure\__init__.py", line 869, in cnPeptideBond cn[1].residue.phi = phi File "C:\Program Files\Chimera 1.10.1\share\chimera\phipsi.py", line 91, in setPhi _setAngle(bond, phi, getPhi(res), "phi") File "C:\Program Files\Chimera 1.10.1\share\chimera\phipsi.py", line 134, in _setAngle br.angle = (newAngle - curAngle, br.biggerSide())TypeError: unsupported operand type(s) for -: 'float' and 'NoneType' TypeError: unsupported operand type(s) for -: 'float' and 'NoneType' File "C:\Program Files\Chimera 1.10.1\share\chimera\phipsi.py", line 134, in _setAngle br.angle = (newAngle - curAngle, br.biggerSide()) My first question is how to solve this error. Second, how can I optimize the generated PDB file using Chimera? I want also to convert this optimize PDB file to PQR. Any advice is greatly appreciated.